The present invention relates to a technique for detecting breakage of light emitting elements and controlling power feeding to light emitting elements.
A turn signal lamp is raised as an automobile lamp which repeatedly flashes at predetermined flashing intervals, and the regulation requires that a breakage of the lamp needs to be detected so that the operating conditions of the lamp can easily be noticed the driver of a vehicle. For example, a function of detecting a breakage of a incandescent lamp is incorporated in a relay flasher circuit (a flasher circuit), and in this breakage detecting function, a reduction in the value of current flowing to an incandescent lamp is used to determine whether or not there exists a breakage.
Incidentally, as a light source other than incandescent lamps, lamps using light emitting elements such as LEDs (light emitting diodes) have been in demand from viewpoints of making lamps thinner or smaller in height and reducing power consumption, or due to needs deriving from the design of vehicles. Then, when light emitting elements are used, since the consumed current and current-voltage characteristics of light emitting elements are different from those of incandescent lamps, a flasher circuit having a breakage detecting function needs to be designed newly.
However, the types and numbers of light emitting elements to be used depend on lamps, and therefore, there are caused problems that in case flashers are newly designed depending on lamps, components control and maintenance become complicated and troublesome, and costs are increased in the case of small-volume production.